| /* FTP extension for IP connection tracking. */ |
| |
| /* (C) 1999-2001 Paul `Rusty' Russell |
| * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org> |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License version 2 as |
| * published by the Free Software Foundation. |
| */ |
| |
| #include <linux/config.h> |
| #include <linux/module.h> |
| #include <linux/netfilter.h> |
| #include <linux/ip.h> |
| #include <linux/ctype.h> |
| #include <net/checksum.h> |
| #include <net/tcp.h> |
| |
| #include <linux/netfilter_ipv4/ip_conntrack_helper.h> |
| #include <linux/netfilter_ipv4/ip_conntrack_ftp.h> |
| #include <linux/moduleparam.h> |
| |
| MODULE_LICENSE("GPL"); |
| MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>"); |
| MODULE_DESCRIPTION("ftp connection tracking helper"); |
| |
| /* This is slow, but it's simple. --RR */ |
| static char ftp_buffer[65536]; |
| |
| static DEFINE_SPINLOCK(ip_ftp_lock); |
| |
| #define MAX_PORTS 8 |
| static int ports[MAX_PORTS]; |
| static int ports_c; |
| module_param_array(ports, int, &ports_c, 0400); |
| |
| static int loose; |
| module_param(loose, int, 0600); |
| |
| unsigned int (*ip_nat_ftp_hook)(struct sk_buff **pskb, |
| enum ip_conntrack_info ctinfo, |
| enum ip_ct_ftp_type type, |
| unsigned int matchoff, |
| unsigned int matchlen, |
| struct ip_conntrack_expect *exp, |
| u32 *seq); |
| EXPORT_SYMBOL_GPL(ip_nat_ftp_hook); |
| |
| #if 0 |
| #define DEBUGP printk |
| #else |
| #define DEBUGP(format, args...) |
| #endif |
| |
| static int try_rfc959(const char *, size_t, u_int32_t [], char); |
| static int try_eprt(const char *, size_t, u_int32_t [], char); |
| static int try_epsv_response(const char *, size_t, u_int32_t [], char); |
| |
| static struct ftp_search { |
| enum ip_conntrack_dir dir; |
| const char *pattern; |
| size_t plen; |
| char skip; |
| char term; |
| enum ip_ct_ftp_type ftptype; |
| int (*getnum)(const char *, size_t, u_int32_t[], char); |
| } search[] = { |
| { |
| IP_CT_DIR_ORIGINAL, |
| "PORT", sizeof("PORT") - 1, ' ', '\r', |
| IP_CT_FTP_PORT, |
| try_rfc959, |
| }, |
| { |
| IP_CT_DIR_REPLY, |
| "227 ", sizeof("227 ") - 1, '(', ')', |
| IP_CT_FTP_PASV, |
| try_rfc959, |
| }, |
| { |
| IP_CT_DIR_ORIGINAL, |
| "EPRT", sizeof("EPRT") - 1, ' ', '\r', |
| IP_CT_FTP_EPRT, |
| try_eprt, |
| }, |
| { |
| IP_CT_DIR_REPLY, |
| "229 ", sizeof("229 ") - 1, '(', ')', |
| IP_CT_FTP_EPSV, |
| try_epsv_response, |
| }, |
| }; |
| |
| static int try_number(const char *data, size_t dlen, u_int32_t array[], |
| int array_size, char sep, char term) |
| { |
| u_int32_t i, len; |
| |
| memset(array, 0, sizeof(array[0])*array_size); |
| |
| /* Keep data pointing at next char. */ |
| for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) { |
| if (*data >= '0' && *data <= '9') { |
| array[i] = array[i]*10 + *data - '0'; |
| } |
| else if (*data == sep) |
| i++; |
| else { |
| /* Unexpected character; true if it's the |
| terminator and we're finished. */ |
| if (*data == term && i == array_size - 1) |
| return len; |
| |
| DEBUGP("Char %u (got %u nums) `%u' unexpected\n", |
| len, i, *data); |
| return 0; |
| } |
| } |
| DEBUGP("Failed to fill %u numbers separated by %c\n", array_size, sep); |
| |
| return 0; |
| } |
| |
| /* Returns 0, or length of numbers: 192,168,1,1,5,6 */ |
| static int try_rfc959(const char *data, size_t dlen, u_int32_t array[6], |
| char term) |
| { |
| return try_number(data, dlen, array, 6, ',', term); |
| } |
| |
| /* Grab port: number up to delimiter */ |
| static int get_port(const char *data, int start, size_t dlen, char delim, |
| u_int32_t array[2]) |
| { |
| u_int16_t port = 0; |
| int i; |
| |
| for (i = start; i < dlen; i++) { |
| /* Finished? */ |
| if (data[i] == delim) { |
| if (port == 0) |
| break; |
| array[0] = port >> 8; |
| array[1] = port; |
| return i + 1; |
| } |
| else if (data[i] >= '0' && data[i] <= '9') |
| port = port*10 + data[i] - '0'; |
| else /* Some other crap */ |
| break; |
| } |
| return 0; |
| } |
| |
| /* Returns 0, or length of numbers: |1|132.235.1.2|6275| */ |
| static int try_eprt(const char *data, size_t dlen, u_int32_t array[6], |
| char term) |
| { |
| char delim; |
| int length; |
| |
| /* First character is delimiter, then "1" for IPv4, then |
| delimiter again. */ |
| if (dlen <= 3) return 0; |
| delim = data[0]; |
| if (isdigit(delim) || delim < 33 || delim > 126 |
| || data[1] != '1' || data[2] != delim) |
| return 0; |
| |
| DEBUGP("EPRT: Got |1|!\n"); |
| /* Now we have IP address. */ |
| length = try_number(data + 3, dlen - 3, array, 4, '.', delim); |
| if (length == 0) |
| return 0; |
| |
| DEBUGP("EPRT: Got IP address!\n"); |
| /* Start offset includes initial "|1|", and trailing delimiter */ |
| return get_port(data, 3 + length + 1, dlen, delim, array+4); |
| } |
| |
| /* Returns 0, or length of numbers: |||6446| */ |
| static int try_epsv_response(const char *data, size_t dlen, u_int32_t array[6], |
| char term) |
| { |
| char delim; |
| |
| /* Three delimiters. */ |
| if (dlen <= 3) return 0; |
| delim = data[0]; |
| if (isdigit(delim) || delim < 33 || delim > 126 |
| || data[1] != delim || data[2] != delim) |
| return 0; |
| |
| return get_port(data, 3, dlen, delim, array+4); |
| } |
| |
| /* Return 1 for match, 0 for accept, -1 for partial. */ |
| static int find_pattern(const char *data, size_t dlen, |
| const char *pattern, size_t plen, |
| char skip, char term, |
| unsigned int *numoff, |
| unsigned int *numlen, |
| u_int32_t array[6], |
| int (*getnum)(const char *, size_t, u_int32_t[], char)) |
| { |
| size_t i; |
| |
| DEBUGP("find_pattern `%s': dlen = %u\n", pattern, dlen); |
| if (dlen == 0) |
| return 0; |
| |
| if (dlen <= plen) { |
| /* Short packet: try for partial? */ |
| if (strnicmp(data, pattern, dlen) == 0) |
| return -1; |
| else return 0; |
| } |
| |
| if (strnicmp(data, pattern, plen) != 0) { |
| #if 0 |
| size_t i; |
| |
| DEBUGP("ftp: string mismatch\n"); |
| for (i = 0; i < plen; i++) { |
| DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n", |
| i, data[i], data[i], |
| pattern[i], pattern[i]); |
| } |
| #endif |
| return 0; |
| } |
| |
| DEBUGP("Pattern matches!\n"); |
| /* Now we've found the constant string, try to skip |
| to the 'skip' character */ |
| for (i = plen; data[i] != skip; i++) |
| if (i == dlen - 1) return -1; |
| |
| /* Skip over the last character */ |
| i++; |
| |
| DEBUGP("Skipped up to `%c'!\n", skip); |
| |
| *numoff = i; |
| *numlen = getnum(data + i, dlen - i, array, term); |
| if (!*numlen) |
| return -1; |
| |
| DEBUGP("Match succeeded!\n"); |
| return 1; |
| } |
| |
| /* Look up to see if we're just after a \n. */ |
| static int find_nl_seq(u32 seq, const struct ip_ct_ftp_master *info, int dir) |
| { |
| unsigned int i; |
| |
| for (i = 0; i < info->seq_aft_nl_num[dir]; i++) |
| if (info->seq_aft_nl[dir][i] == seq) |
| return 1; |
| return 0; |
| } |
| |
| /* We don't update if it's older than what we have. */ |
| static void update_nl_seq(u32 nl_seq, struct ip_ct_ftp_master *info, int dir) |
| { |
| unsigned int i, oldest = NUM_SEQ_TO_REMEMBER; |
| |
| /* Look for oldest: if we find exact match, we're done. */ |
| for (i = 0; i < info->seq_aft_nl_num[dir]; i++) { |
| if (info->seq_aft_nl[dir][i] == nl_seq) |
| return; |
| |
| if (oldest == info->seq_aft_nl_num[dir] |
| || before(info->seq_aft_nl[dir][i], oldest)) |
| oldest = i; |
| } |
| |
| if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) |
| info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq; |
| else if (oldest != NUM_SEQ_TO_REMEMBER) |
| info->seq_aft_nl[dir][oldest] = nl_seq; |
| } |
| |
| static int help(struct sk_buff **pskb, |
| struct ip_conntrack *ct, |
| enum ip_conntrack_info ctinfo) |
| { |
| unsigned int dataoff, datalen; |
| struct tcphdr _tcph, *th; |
| char *fb_ptr; |
| int ret; |
| u32 seq, array[6] = { 0 }; |
| int dir = CTINFO2DIR(ctinfo); |
| unsigned int matchlen, matchoff; |
| struct ip_ct_ftp_master *ct_ftp_info = &ct->help.ct_ftp_info; |
| struct ip_conntrack_expect *exp; |
| unsigned int i; |
| int found = 0, ends_in_nl; |
| |
| /* Until there's been traffic both ways, don't look in packets. */ |
| if (ctinfo != IP_CT_ESTABLISHED |
| && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) { |
| DEBUGP("ftp: Conntrackinfo = %u\n", ctinfo); |
| return NF_ACCEPT; |
| } |
| |
| th = skb_header_pointer(*pskb, (*pskb)->nh.iph->ihl*4, |
| sizeof(_tcph), &_tcph); |
| if (th == NULL) |
| return NF_ACCEPT; |
| |
| dataoff = (*pskb)->nh.iph->ihl*4 + th->doff*4; |
| /* No data? */ |
| if (dataoff >= (*pskb)->len) { |
| DEBUGP("ftp: pskblen = %u\n", (*pskb)->len); |
| return NF_ACCEPT; |
| } |
| datalen = (*pskb)->len - dataoff; |
| |
| spin_lock_bh(&ip_ftp_lock); |
| fb_ptr = skb_header_pointer(*pskb, dataoff, |
| (*pskb)->len - dataoff, ftp_buffer); |
| BUG_ON(fb_ptr == NULL); |
| |
| ends_in_nl = (fb_ptr[datalen - 1] == '\n'); |
| seq = ntohl(th->seq) + datalen; |
| |
| /* Look up to see if we're just after a \n. */ |
| if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) { |
| /* Now if this ends in \n, update ftp info. */ |
| DEBUGP("ip_conntrack_ftp_help: wrong seq pos %s(%u) or %s(%u)\n", |
| ct_ftp_info->seq_aft_nl[0][dir] |
| old_seq_aft_nl_set ? "":"(UNSET) ", old_seq_aft_nl); |
| ret = NF_ACCEPT; |
| goto out_update_nl; |
| } |
| |
| /* Initialize IP array to expected address (it's not mentioned |
| in EPSV responses) */ |
| array[0] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 24) & 0xFF; |
| array[1] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 16) & 0xFF; |
| array[2] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 8) & 0xFF; |
| array[3] = ntohl(ct->tuplehash[dir].tuple.src.ip) & 0xFF; |
| |
| for (i = 0; i < ARRAY_SIZE(search); i++) { |
| if (search[i].dir != dir) continue; |
| |
| found = find_pattern(fb_ptr, (*pskb)->len - dataoff, |
| search[i].pattern, |
| search[i].plen, |
| search[i].skip, |
| search[i].term, |
| &matchoff, &matchlen, |
| array, |
| search[i].getnum); |
| if (found) break; |
| } |
| if (found == -1) { |
| /* We don't usually drop packets. After all, this is |
| connection tracking, not packet filtering. |
| However, it is necessary for accurate tracking in |
| this case. */ |
| if (net_ratelimit()) |
| printk("conntrack_ftp: partial %s %u+%u\n", |
| search[i].pattern, |
| ntohl(th->seq), datalen); |
| ret = NF_DROP; |
| goto out; |
| } else if (found == 0) { /* No match */ |
| ret = NF_ACCEPT; |
| goto out_update_nl; |
| } |
| |
| DEBUGP("conntrack_ftp: match `%s' (%u bytes at %u)\n", |
| fb_ptr + matchoff, matchlen, ntohl(th->seq) + matchoff); |
| |
| /* Allocate expectation which will be inserted */ |
| exp = ip_conntrack_expect_alloc(); |
| if (exp == NULL) { |
| ret = NF_DROP; |
| goto out; |
| } |
| |
| /* We refer to the reverse direction ("!dir") tuples here, |
| * because we're expecting something in the other direction. |
| * Doesn't matter unless NAT is happening. */ |
| exp->tuple.dst.ip = ct->tuplehash[!dir].tuple.dst.ip; |
| |
| if (htonl((array[0] << 24) | (array[1] << 16) | (array[2] << 8) | array[3]) |
| != ct->tuplehash[dir].tuple.src.ip) { |
| /* Enrico Scholz's passive FTP to partially RNAT'd ftp |
| server: it really wants us to connect to a |
| different IP address. Simply don't record it for |
| NAT. */ |
| DEBUGP("conntrack_ftp: NOT RECORDING: %u,%u,%u,%u != %u.%u.%u.%u\n", |
| array[0], array[1], array[2], array[3], |
| NIPQUAD(ct->tuplehash[dir].tuple.src.ip)); |
| |
| /* Thanks to Cristiano Lincoln Mattos |
| <lincoln@cesar.org.br> for reporting this potential |
| problem (DMZ machines opening holes to internal |
| networks, or the packet filter itself). */ |
| if (!loose) { |
| ret = NF_ACCEPT; |
| ip_conntrack_expect_free(exp); |
| goto out_update_nl; |
| } |
| exp->tuple.dst.ip = htonl((array[0] << 24) | (array[1] << 16) |
| | (array[2] << 8) | array[3]); |
| } |
| |
| exp->tuple.src.ip = ct->tuplehash[!dir].tuple.src.ip; |
| exp->tuple.dst.u.tcp.port = htons(array[4] << 8 | array[5]); |
| exp->tuple.src.u.tcp.port = 0; /* Don't care. */ |
| exp->tuple.dst.protonum = IPPROTO_TCP; |
| exp->mask = ((struct ip_conntrack_tuple) |
| { { 0xFFFFFFFF, { 0 } }, |
| { 0xFFFFFFFF, { .tcp = { 0xFFFF } }, 0xFF }}); |
| |
| exp->expectfn = NULL; |
| exp->master = ct; |
| |
| /* Now, NAT might want to mangle the packet, and register the |
| * (possibly changed) expectation itself. */ |
| if (ip_nat_ftp_hook) |
| ret = ip_nat_ftp_hook(pskb, ctinfo, search[i].ftptype, |
| matchoff, matchlen, exp, &seq); |
| else { |
| /* Can't expect this? Best to drop packet now. */ |
| if (ip_conntrack_expect_related(exp) != 0) { |
| ip_conntrack_expect_free(exp); |
| ret = NF_DROP; |
| } else |
| ret = NF_ACCEPT; |
| } |
| |
| out_update_nl: |
| /* Now if this ends in \n, update ftp info. Seq may have been |
| * adjusted by NAT code. */ |
| if (ends_in_nl) |
| update_nl_seq(seq, ct_ftp_info,dir); |
| out: |
| spin_unlock_bh(&ip_ftp_lock); |
| return ret; |
| } |
| |
| static struct ip_conntrack_helper ftp[MAX_PORTS]; |
| static char ftp_names[MAX_PORTS][10]; |
| |
| /* Not __exit: called from init() */ |
| static void fini(void) |
| { |
| int i; |
| for (i = 0; i < ports_c; i++) { |
| DEBUGP("ip_ct_ftp: unregistering helper for port %d\n", |
| ports[i]); |
| ip_conntrack_helper_unregister(&ftp[i]); |
| } |
| } |
| |
| static int __init init(void) |
| { |
| int i, ret; |
| char *tmpname; |
| |
| if (ports_c == 0) |
| ports[ports_c++] = FTP_PORT; |
| |
| for (i = 0; i < ports_c; i++) { |
| ftp[i].tuple.src.u.tcp.port = htons(ports[i]); |
| ftp[i].tuple.dst.protonum = IPPROTO_TCP; |
| ftp[i].mask.src.u.tcp.port = 0xFFFF; |
| ftp[i].mask.dst.protonum = 0xFF; |
| ftp[i].max_expected = 1; |
| ftp[i].timeout = 5 * 60; /* 5 minutes */ |
| ftp[i].me = THIS_MODULE; |
| ftp[i].help = help; |
| |
| tmpname = &ftp_names[i][0]; |
| if (ports[i] == FTP_PORT) |
| sprintf(tmpname, "ftp"); |
| else |
| sprintf(tmpname, "ftp-%d", ports[i]); |
| ftp[i].name = tmpname; |
| |
| DEBUGP("ip_ct_ftp: registering helper for port %d\n", |
| ports[i]); |
| ret = ip_conntrack_helper_register(&ftp[i]); |
| |
| if (ret) { |
| fini(); |
| return ret; |
| } |
| } |
| return 0; |
| } |
| |
| module_init(init); |
| module_exit(fini); |